材料期刊网

Computerized Simulation on the Structure of Cryolite-Alumina Melts

XIE Gang , QIU Zhuxian , XU Chi , CHEN Nainyi Northeast University of Technology , Shenyang , China. Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China. To whom correspondence should be addressed.

材料科学技术（英文）

Monte Carlo calculations were performed on liquid ionic solution of saturated alumina in cryolite melt containing a total of 205 ions. The local structure and radial distribution functions of the melt were computerized by Monte Carlo method at 1283 K. It has been found that there exist the complex ionic clusters such as AlOF_3~(2-), AlOF_4~(3-), AlF_4~-, AlF_5~(2-), AlOF_2~- etc., as well as oxygen-bridge and flourine-bridge ionic clusters. In the melt studied, Al~(3+) ions tend to have preferential even coordination number of 4F~- ions.

关键词: Monte Carlo method , null , null , null , null

Fracture Analysis of Composites in High-speed Tension

JIANG Chiping , CAO Li , ZOU Zhenzhu , WANG Duo , YAO Zhongkai Harbin Institute of Technology , Harbin , China. To whom correspondence should be addressed.

材料科学技术（英文）

In this paper the results of a high-speed tension experiment of the SiC_w/Al composite have been reported and a simplified theoretical model has been developed to study the fracture mechanism of composites in high-speed tension. This theoretical model provides a new explanation for the increase of dynamic fracture strength of composites in high-speed tension.

关键词: composite material , null , null , null

The Mssbauer Effect of Y-Ba-Cu-Fe-O Superconductive Oxide

XIA Sike , MA Ruzhang , CAO Guohui , LI Zhengwen , FENG Yongrong University of Science and Technology , Beijing , China. To whom correspondence should be addressed.

材料科学技术（英文）

We have studied the Mossbauer effect of YBa_2Cu_(2.88)Fe_(0.12)O_(7-x) superconductive oxide from 78 to 273K. Two minima of recoilless fraction and Debye temperature were found near 110K and 220K. It means that lattice softening happened near these two temperatures. We also observed minima of isomer shift near 110K and quadrupole splitting increase when temperature is lower than 110K. We suggest that lattice softening would lead to the displacement of oxygen atoms. This may be relative to superconductive transition.

关键词: Y-Ba-Cu-Fe-O superconductor , null , null

Influence of Carbon Content and Solidification Condition on Incipient Melting of DS Superalloy MAR-M200+2Hf

ZHENG Yunrong , WANG Luobao , LI Chenggong Institute of Aeronautical Naterials , Beijing , China. To whom correspondence should be addressed.

材料科学技术（英文）

Hf lowers the incipient melting temperature of superalloy. As carbon content in Hf-bearing alloy decreases, the incipient melting temperature drops furthey. PD ingots have stronger tendency to incipient melting than HRS ones. Even though in PD ingot, the sensitivities at both ends of the ingot are quite different. The melting of Ni_5Hf phase may be considered as one of the main factors affecting incipient melting. The more Ni_5Hf the alloy contains, the more serious the incipient melting becomes. The results of differential thermal analysis (DTA) have proved that the peak of 1135-1160℃ corresponds to the melting range or Ni_5Hf. By means of a pretreatment at 1150℃, 8h, Ni_5Hf phase can be eliminated in two ways: the reaction Ni_5Hf+γ(C)→MC_(2)+γ and solid solution, and therefore the final solid solution treatment can be carried out at 1260℃. This brings about a high homogenized structure and further increases the stress rupture properties of the alloy at 1040℃, 140 MPa.

关键词: DS superalloy , null , null , null , null , null

The Study of Dual-phase Steel after Cyclic Deformation at Various Strain Amplitudes

SUN Zhengming , WANG Zhongguang , AI Suhua Institute of Metal Research , Academia Sinica , Shenyang , China. To whom correspondence should be addressed.

材料科学技术（英文）

Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-% martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.

关键词: cyclic deformation , null , null

A Statistical Model of Quantitative Relationship between Striation Spacings and Fatigue Crack Growth Rates

YANG Jingjun , KE Wei Institute of Corrosion and Protection of Metals , Academia Sinica , Shenyang , China. To whom correspondence should be addressed.

材料科学技术（英文）

Fatigue crack growth experiments were per- formed on A1 alloy LD 10 and Ti-6A1-4V alloy. Fatigue striation spacings and the deviation angles between the direction of micro-crack growth and that of macro-crack growth were quanti- tatively measured on fracture surface using scanning electron microscope. A statistical model of the relationship between striation spacings and fatigue crack propagation rates was developed on the basis of a statistical analysis of the deviation angles, Good agreement between experimental results and theoretical results calculated with the present model was obtained.

关键词: striation spacing , null , null

Creep Deformation and Rupture in Smooth and Notched Specimens in HK40 Steel

ZHU Shijie , ZHAO Jie , WANG Fugang , CAO Zhiben Dalian University of Technology , Liaoning , China. To whom correspondence should be addressed.

材料科学技术（英文）

The effects of the eutectic carbides rand secondary carbides on creep deformation and rupture in smooth bars and CT specimens have been studied. The results show that the resistance of the eutectic carbides of skeleton shape to crack growth is larger than that of the blocky shape carbides. The dendritic segregation of secondary carbides promotes the creep ductility. As the secondary carbide particles become coarser, the creep ductility increases and the crack growth rate decreases. However, if the size of secondary carbide is too large, the creep strength decreases too much and therefore crack growth rate increases.

关键词: creep , null , null , null

Microstructure and Coercivity in High H_c Sm(Co, Cu, Fe, Zr)_(7.4) and Nd-Fe-B Alloys

PAN Shuming , XIAO Yaofu General Research Institute of Nonferrous Metals , CNNC. Beijing , China. University of Science and Technology Beijing , China. To whom correspondence should be addressed.

材料科学技术（英文）

关键词: HVEM observation , null , null